Not Applicable
Not Applicable
The invention relates to a temperature-adjusted sampler for fluids, gases or other fluids.
Temperature-adjusted samplers are particularly used in automatic and semiautomatic analyzers for medical science, bio-engineering, environment analytical chemistry, and substance analyses in which liquid, gaseous or other fluid samples or reagents are received, transported, and discharged.
The samples may be adjusted in temperature by means of the temperature-adjusted sampler here. For example, this may be necessary for endogenous liquids, substances or materials which require to be kept to body temperature.
Problems will frequently occur in temperature adjustment, liquid detection, blending, etc. of the samples.
Some known systems and their drawbacks will now be presented:
A hollow needle with a cavity through which temperature-adjusted water or another liquid for adjusting the needle temperature is pumped. The drawback of this system is the growth of bacteria in the temperature-adjusting liquid, which frequently needs to be exchanged for this reason even if it contains additives to prevent the growth of bacteria. Since the exchange of the temperature-adjusting liquid cannot be carried out by the user the servicing expenses are high. Furthermore, the expenditure in devices is high in this system. Adjusting the temperature up to the tip of the hollow needle is impossible because the cavity does not extend up to the tip.
Further, there are hollow needles which are heated by means of a deposited copper jacket using foil heating or a heating coil. The foil heating consists of a foil having a heating layer laminated thereon. The electric conductivity if the foil is relatively bad. The foil heating can only be adhered to hollow needles having a relatively large diameter. The adhesive bond of the foil heating can easily be detached. A further drawback is that heat transfer is too sluggish if cooling (i.e. by ambient temperature) and heating is effected alternately. Furthermore, the outer diameter of the hollow needle is too large with the coatings deposited. Faults in heating and in level detection may arise due to penetrating moisture because of a capillary effect. Precise temperature adjustment up to the tip is impossible and temperature guidance is poor. Another drawback are the great sluggishness, low constancy, and expensive design of this system.
In addition, there are hollow needles using a directly deposited heating coil. Here, the drawbacks only are the linearly shaped heat transfer and too slow and too sluggish a temperture guidance, which mostly necessitates separate pre-heating components. The temperature transient response of this system is unfavourable as well and requires expenditure in temperature regulation.
Due to their construction, all of the aforementioned systems have a large outer diameter so that a relatively long, non-temperature adjusted needle tip is required to dip them into small sample vessels. As a result, very small sample volumes can be treated only conditionally or cannot be treated. Because of their construction, faults in heating and in level detection will frequently occur because of the penetration of moisture or capillary effects. The reasons are the many mechanically assembled components, glued joints, shrunk-on flexible tubes and the like. The two last-mentioned systems using a heating wire or heating foils only have a linearly shaped heat transfer zone and, consequently, are sluggish and inaccurate.
All above mentioned embodiments have the disadvantage that they largely increase the outer diameter of the sampler and heat transfer is relatively slow. The non-heated needle tip which is very long does not allow of precise temperature adjustment, particulary for small sample volumes.
More problems of previous systems are:
Separate stirring devices are used to blend substances. If these have to be displaced as well they will impede any further acceleration of the displacing motions or extend the time for analyses and are expensive.
Piercing through the lids of closed vessels is effected only via separate pre-piercing devices which require increased expenditure in construction and higher expenses for the devices.
Substance entrainments and level detection problems occur because of the multiplicity of components and glued joints, shrunk-on flexible tubes, sensor wires and the like of the previous samplers. The sharp edges, corners, and capillary structures of the former systems may cause substance entrainments which can only be prevented by more expensive washings with cleansing liquid. Longer washing times imply longer cycle times of the analytical instrument end increase the demand of cleansing liquid and the expenditure in disposal. Moisture penetrations into the capillaries may prevent the function of level detection.
Any device to detect needle pluggings has been integrated in very few analytical instruments hitherto and requires great expenditure. Particularly in measuring blood coagulation, there is an increased risk of plugging, which may lead to erroneous measurements and increased times of failure.
Therefore, it is an object of the invention to provide an adjusted-temperature sampler which can be designed at less expenditure and in a smaller cross-section and has more favourable characteristics in use.
In the inventive sampler, the coatings deposited only are very thin so that only an insignificant increase in cross-section will arise. Moreover, the heating layer will rest on the insulating layer respectively the hollow needle with its all-over surface unlike a heating coil or a heating foil. As a result, the heating power is transferred very quickly to the internally lying liquid. The insulating layer may completely or almost completely or partly cover the hollow needle and the heating layer may completely or almost completely or partly cover the insulating layer. The insulating layer may be made up, for example, from glass ceramic material, Teflon, diamond, boron nitride or the like. The heating layer may be made up, for example, from known resistive materials (especially for resistors). The heating layer may be made up, for example, from metals, alloys or semiconductors. Preferably, the heating layer shows a high specific resistance and a high temperature coefficient.
Certain features of the inventive sampler are of a particular advantage when temperature adjustment may be somewhat slower. Glass or plastic may be more favourable for the proportioning of certain fluids or may reduce the production cost of the sampler. Further, an insulating layer can be dispensed with in the case of glass or plastic.
A feature of the inventive sampler enables the user to easily exchange the sampler. The device may be an analytical instrument which, in particular, may have a displacement device to be connected to the hollow needle and an electrical supply device for the heating layer. The hollow needle may be detachably connected within an analytical instrument by a bolted joint to a flexible pipetting tube and the flexible pipetting tube may be connected to the displacement device of the analytical instrument.
A feature of the inventive sampler makes it possible to save a temperature sensor. Furthermore, it allows to average a temperature over the length of the electrically conducting heating layer which is disposed very close to the sample so that a good regulation will result.
A calibration feature of the inventive sampler helps ensure that the requirements for accuracy of the coatings of the hollow needle are low.
Almost all samplers are equipped with a liquid or level detection which either:
measures the resistance between two contacts or
measures the capacitance between the hollow needle and the surface of the associated instrument.
The two techniques have some advantages each. In the first one, for example, it cannot be differentiated whether the sampler merely is wetted by a small liquid volume or is dipped. In the second technique, the evaluation of the measuring signal involves relatively great expenditure. Moreover, the surface of the instrument requires to have a good connection to the electrical mass.
A feature of the inventive sampler overcomes the aforementioned difficulties and solves the initially described problems of substance entrainment and level detection. The capacitance is measured according to a principle which simplifies evaluation very much and is adaptable to the various requirements of the software. An electric pulse is provided to the hollow needle here. The rise time of the edge of this pulse is determined by the capacitance between the hollow needle and the electrical mass and by the internal resistance of the pulse. The magnitude of capacity may be determined by measuring the voltage on the hollow needle following a short lag time after the pulse is applied. At this time, the lag time requires to be kept constant.
A feature of the inventive sampler makes it possible to detect the liquid by measuring the resistance. In addition, there is a possibility to combine the capacitive and the resistive liquid detection.
The sampler may operate as a blending device, e.g. in an automatic instrument, in which liquid samples are transferred to a blending duct where reagents are added, and are thoroughly blended. This has been made by a separate mixer hitherto. If the hollow needle is caused to vibrate by an electromagnet or ultrasound the sampler will assume this task.
A feature of the inventive sampler makes it possible to pierce the sampler through a lid and to deeply dip it into a liquid. To this effect, the further coating requires to be very hard. Diamond and boron nitride serve the purpose here, for example.
A feature of the inventive sampler prevents a vacuum from building up after the sampler is pierced through the sample closures, which partly have a very high wall thickness and are made from rubber or similar materials, while the sample is drawn in from the vessel. This can reduce the accuracy of dosage of the sample. The slots will generally not inadmissibly weaken the sampler because this one is of a greater wall thickness anyhow to achieve a high puncturing force and buckle proofness for piercing through the lid. In particular, the slots may be configured as milled sinks. Generally, a single slot is sufficient. Several slots preferably are uniformly spaced around the circumference of the sampler. Preferably, the slots are inclined at an angle to the center of the needle. Hereby, the material of the sample closure (i.e. rubber) is hindered to penetrate and obdurate the slots.
A feature of the inventive sampler makes it possible to detect a plugging of the hollow needle while receiving liquids because a pressure drop may be measured and detected in such case. The pressure sensors may be wire strain gauges, foil-type pressure gauges, and others.
A feature of the inventive sampler integrates the ultrasonic transmitter of claim 16 into the coatings. This manner of ultrasound generation was described in xe2x80x9cNaturexe2x80x9d, vol. 400, page 853. Ultrasound may also be employed to clean the sampler.
A feature of the inventive sampler achieves a safe insulation because so-called pinholes (small-diameter holes) in a part-layer are covered by an adjoining part-layer. This utilizes the fact that it is extremely unlikely for pinholes to occur at the same point in the part-layers that cover each other.